Chapter 8
An Open path is one where all of the variables on the path are allowed to vary (e.g. are not one fixed value), and a Closed path is one where at least one variable on the path has a fixed value (e.g. if you controlled for a variable by only having one value of the variable in an experiment, any paths that use that variable would be Closed).
a- X -> A -> Y X <- B -> Y X <- B <- D -> Y X -> C -> D <- Y X -> C <- D -> B -> Y
b- The front door paths are: X -> A -> Y
c- The open back door paths are: X <- B -> Y X <- B <- D -> Y X -> C -> D <- Y X -> C <- D -> B -> Y
d- C and D must be controlled since they are colliders
a-
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